Thursday, November 30, 2023, 16:00
WHGA Auditorium
Attila Krasznahorkay, HUN-REN Institute for Nuclear Research (ATOMKI), Debrecen, Hungary
Abstract:
After introducing our institute I will give a short overview of the
present experimental possibilities and future plans of the institute.
I will focus on some recently published interesting results on the anomalous internal pair creation coefficient of the 18.15 MeV electromagnetic transition of the 8Be nucleus [1]. We found a peak-like deviation in the angular correlation of the e+e- pairs formed in the above transition at large angles (at 140 degrees), which we explained by the creation and decay of a new hypothetical particle. This particle was later named X17 in the literature. Our article has attracted a lot of international interest, and got more than 450, mostly theoretical citations. Many experiments have been planned to demonstrate it, and two groups already reported on supporting the experimental results.
In the present talk, I will summarize our experimental results obtained so far for X17 in 8Be [1], 4He [2] and 12C [3] nuclei. The energy of these nuclear transitions are different, and the observed anomalies appeared at different angles, thereby providing kinematic evidence for the existence of the X17 particle. I will also give a short overview about the theoretical interpretation of the particle as well.
At the end, some preliminary results will be presented, which we obtained in the decay of the electric Giant Dipole Resonance (GDR). They are also consistent with the assumption of the X17 particle. Since the GDR have been observed in all nuclei, our result may pave the way for a systematic nuclear physics study of the X17 particle.
[1] A.J. Krasznahorkay et al., Phys. Rev. Lett. Phys. Rev. Lett. 116,
042501 (2016).
[2] A.J. Krasznahorkay et al., Phys. Rev. C 104, 044003 (2021).
[3] A.J. Krasznahorkay et al., Phys. Rev. C 106, L061601 (2022).